content: // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf;
  
  import java.lang.reflect.Field;
  import java.nio.Buffer;
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  import java.security.AccessController;
  import java.security.PrivilegedExceptionAction;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  /** Utility class for working with unsafe operations. */
  final class UnsafeUtil {
    private static final Logger logger = Logger.getLogger(UnsafeUtil.class.getName());
    private static final sun.misc.Unsafe UNSAFE = getUnsafe();
    private static final MemoryAccessor MEMORY_ACCESSOR = getMemoryAccessor();
    private static final boolean HAS_UNSAFE_BYTEBUFFER_OPERATIONS =
        supportsUnsafeByteBufferOperations();
    private static final boolean HAS_UNSAFE_ARRAY_OPERATIONS = supportsUnsafeArrayOperations();
  
    private static final long BYTE_ARRAY_BASE_OFFSET = arrayBaseOffset(byte[].class);
    // Micro-optimization: we can assume a scale of 1 and skip the multiply
    // private static final long BYTE_ARRAY_INDEX_SCALE = 1;
  
    private static final long BOOLEAN_ARRAY_BASE_OFFSET = arrayBaseOffset(boolean[].class);
    private static final long BOOLEAN_ARRAY_INDEX_SCALE = arrayIndexScale(boolean[].class);
  
    private static final long INT_ARRAY_BASE_OFFSET = arrayBaseOffset(int[].class);
    private static final long INT_ARRAY_INDEX_SCALE = arrayIndexScale(int[].class);
  
    private static final long LONG_ARRAY_BASE_OFFSET = arrayBaseOffset(long[].class);
    private static final long LONG_ARRAY_INDEX_SCALE = arrayIndexScale(long[].class);
  
    private static final long FLOAT_ARRAY_BASE_OFFSET = arrayBaseOffset(float[].class);
    private static final long FLOAT_ARRAY_INDEX_SCALE = arrayIndexScale(float[].class);
  
    private static final long DOUBLE_ARRAY_BASE_OFFSET = arrayBaseOffset(double[].class);
    private static final long DOUBLE_ARRAY_INDEX_SCALE = arrayIndexScale(double[].class);
  
    private static final long OBJECT_ARRAY_BASE_OFFSET = arrayBaseOffset(Object[].class);
    private static final long OBJECT_ARRAY_INDEX_SCALE = arrayIndexScale(Object[].class);
  
    private static final long BUFFER_ADDRESS_OFFSET = fieldOffset(bufferAddressField());
  
    private static final long STRING_VALUE_OFFSET = fieldOffset(stringValueField());
  
    private UnsafeUtil() {}
  
    static boolean hasUnsafeArrayOperations() {
      return HAS_UNSAFE_ARRAY_OPERATIONS;
    }
  
    static boolean hasUnsafeByteBufferOperations() {
      return HAS_UNSAFE_BYTEBUFFER_OPERATIONS;
    }
  
  
    static long objectFieldOffset(Field field) {
      return MEMORY_ACCESSOR.objectFieldOffset(field);
    }
  
    private static int arrayBaseOffset(Class<?> clazz) {
      return HAS_UNSAFE_ARRAY_OPERATIONS ? MEMORY_ACCESSOR.arrayBaseOffset(clazz) : -1;
    }
  
    private static int arrayIndexScale(Class<?> clazz) {
      return HAS_UNSAFE_ARRAY_OPERATIONS ? MEMORY_ACCESSOR.arrayIndexScale(clazz) : -1;
    }
  
    static byte getByte(Object target, long offset) {
      return MEMORY_ACCESSOR.getByte(target, offset);
    }
  
    static void putByte(Object target, long offset, byte value) {
      MEMORY_ACCESSOR.putByte(target, offset, value);
    }
  
    static int getInt(Object target, long offset) {
      return MEMORY_ACCESSOR.getInt(target, offset);
    }
  
    static void putInt(Object target, long offset, int value) {
      MEMORY_ACCESSOR.putInt(target, offset, value);
    }
  
    static long getLong(Object target, long offset) {
      return MEMORY_ACCESSOR.getLong(target, offset);
    }
  
    static void putLong(Object target, long offset, long value) {
      MEMORY_ACCESSOR.putLong(target, offset, value);
    }
  
    static boolean getBoolean(Object target, long offset) {
      return MEMORY_ACCESSOR.getBoolean(target, offset);
    }
  
    static void putBoolean(Object target, long offset, boolean value) {
      MEMORY_ACCESSOR.putBoolean(target, offset, value);
    }
  
    static float getFloat(Object target, long offset) {
      return MEMORY_ACCESSOR.getFloat(target, offset);
    }
  
    static void putFloat(Object target, long offset, float value) {
      MEMORY_ACCESSOR.putFloat(target, offset, value);
    }
  
    static double getDouble(Object target, long offset) {
      return MEMORY_ACCESSOR.getDouble(target, offset);
    }
  
    static void putDouble(Object target, long offset, double value) {
      MEMORY_ACCESSOR.putDouble(target, offset, value);
    }
  
    static Object getObject(Object target, long offset) {
      return MEMORY_ACCESSOR.getObject(target, offset);
    }
  
    static void putObject(Object target, long offset, Object value) {
      MEMORY_ACCESSOR.putObject(target, offset, value);
    }
  
    static byte getByte(byte[] target, long index) {
      return MEMORY_ACCESSOR.getByte(target, BYTE_ARRAY_BASE_OFFSET + index);
    }
  
    static void putByte(byte[] target, long index, byte value) {
      MEMORY_ACCESSOR.putByte(target, BYTE_ARRAY_BASE_OFFSET + index, value);
    }
  
    static int getInt(int[] target, long index) {
      return MEMORY_ACCESSOR.getInt(target, INT_ARRAY_BASE_OFFSET + (index * INT_ARRAY_INDEX_SCALE));
    }
  
    static void putInt(int[] target, long index, int value) {
      MEMORY_ACCESSOR.putInt(target, INT_ARRAY_BASE_OFFSET + (index * INT_ARRAY_INDEX_SCALE), value);
    }
  
    static long getLong(long[] target, long index) {
      return MEMORY_ACCESSOR.getLong(
          target, LONG_ARRAY_BASE_OFFSET + (index * LONG_ARRAY_INDEX_SCALE));
    }
  
    static void putLong(long[] target, long index, long value) {
      MEMORY_ACCESSOR.putLong(
          target, LONG_ARRAY_BASE_OFFSET + (index * LONG_ARRAY_INDEX_SCALE), value);
    }
  
    static boolean getBoolean(boolean[] target, long index) {
      return MEMORY_ACCESSOR.getBoolean(
          target, BOOLEAN_ARRAY_BASE_OFFSET + (index * BOOLEAN_ARRAY_INDEX_SCALE));
    }
  
    static void putBoolean(boolean[] target, long index, boolean value) {
      MEMORY_ACCESSOR.putBoolean(
          target, BOOLEAN_ARRAY_BASE_OFFSET + (index * BOOLEAN_ARRAY_INDEX_SCALE), value);
    }
  
    static float getFloat(float[] target, long index) {
      return MEMORY_ACCESSOR.getFloat(
          target, FLOAT_ARRAY_BASE_OFFSET + (index * FLOAT_ARRAY_INDEX_SCALE));
    }
  
    static void putFloat(float[] target, long index, float value) {
      MEMORY_ACCESSOR.putFloat(
          target, FLOAT_ARRAY_BASE_OFFSET + (index * FLOAT_ARRAY_INDEX_SCALE), value);
    }
  
    static double getDouble(double[] target, long index) {
      return MEMORY_ACCESSOR.getDouble(
          target, DOUBLE_ARRAY_BASE_OFFSET + (index * DOUBLE_ARRAY_INDEX_SCALE));
    }
  
    static void putDouble(double[] target, long index, double value) {
      MEMORY_ACCESSOR.putDouble(
          target, DOUBLE_ARRAY_BASE_OFFSET + (index * DOUBLE_ARRAY_INDEX_SCALE), value);
    }
  
    static Object getObject(Object[] target, long index) {
      return MEMORY_ACCESSOR.getObject(
          target, OBJECT_ARRAY_BASE_OFFSET + (index * OBJECT_ARRAY_INDEX_SCALE));
    }
  
    static void putObject(Object[] target, long index, Object value) {
      MEMORY_ACCESSOR.putObject(
          target, OBJECT_ARRAY_BASE_OFFSET + (index * OBJECT_ARRAY_INDEX_SCALE), value);
    }
  
    static void copyMemory(byte[] src, long srcIndex, long targetOffset, long length) {
      MEMORY_ACCESSOR.copyMemory(src, srcIndex, targetOffset, length);
    }
  
    static void copyMemory(long srcOffset, byte[] target, long targetIndex, long length) {
      MEMORY_ACCESSOR.copyMemory(srcOffset, target, targetIndex, length);
    }
  
    static void copyMemory(byte[] src, long srcIndex, byte[] target, long targetIndex, long length) {
      System.arraycopy(src, (int) srcIndex, target, (int) targetIndex, (int) length); 
    }
  
    static byte getByte(long address) {
      return MEMORY_ACCESSOR.getByte(address);
    }
  
    static void putByte(long address, byte value) {
      MEMORY_ACCESSOR.putByte(address, value);
    }
  
    static int getInt(long address) {
      return MEMORY_ACCESSOR.getInt(address);
    }
  
    static void putInt(long address, int value) {
      MEMORY_ACCESSOR.putInt(address, value);
    }
  
    static long getLong(long address) {
      return MEMORY_ACCESSOR.getLong(address);
    }
  
    static void putLong(long address, long value) {
      MEMORY_ACCESSOR.putLong(address, value);
    }
  
    /**
     * Gets the offset of the {@code address} field of the given direct {@link ByteBuffer}.
     */
    static long addressOffset(ByteBuffer buffer) {
      return MEMORY_ACCESSOR.getLong(buffer, BUFFER_ADDRESS_OFFSET);
    }
  
    /**
     * Returns a new {@link String} backed by the given {@code chars}. The char array should not
     * be mutated any more after calling this function.
     */
    static String moveToString(char[] chars) {
      if (STRING_VALUE_OFFSET == -1) {
        // In the off-chance that this JDK does not implement String as we'd expect, just do a copy.
        return new String(chars);
      }
      final String str;
      try {
        str = (String) UNSAFE.allocateInstance(String.class);
      } catch (InstantiationException e) {
        // This should never happen, but return a copy as a fallback just in case.
        return new String(chars);
      }
      putObject(str, STRING_VALUE_OFFSET, chars);
      return str;
    }
  
    static Object getStaticObject(Field field) {
      return MEMORY_ACCESSOR.getStaticObject(field);
    }
  
    /**
     * Gets the {@code sun.misc.Unsafe} instance, or {@code null} if not available on this platform.
     */
    static sun.misc.Unsafe getUnsafe() {
      sun.misc.Unsafe unsafe = null;
      try {
        unsafe =
            AccessController.doPrivileged(
                new PrivilegedExceptionAction<sun.misc.Unsafe>() {
                  @Override
                  public sun.misc.Unsafe run() throws Exception {
                    Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
  
                    for (Field f : k.getDeclaredFields()) {
                      f.setAccessible(true);
                      Object x = f.get(null);
                      if (k.isInstance(x)) {
                        return k.cast(x);
                      }
                    }
                    // The sun.misc.Unsafe field does not exist.
                    return null;
                  }
                });
      } catch (Throwable e) {
        // Catching Throwable here due to the fact that Google AppEngine raises NoClassDefFoundError
        // for Unsafe.
      }
      return unsafe;
    }
  
    /** Get a {@link MemoryAccessor} appropriate for the platform, or null if not supported. */
    private static MemoryAccessor getMemoryAccessor() {
      if (UNSAFE == null) {
        return null;
      }
      return new JvmMemoryAccessor(UNSAFE);
    }
  
    /** Indicates whether or not unsafe array operations are supported on this platform. */
    private static boolean supportsUnsafeArrayOperations() {
      if (UNSAFE == null) {
        return false;
      }
      try {
        Class<?> clazz = UNSAFE.getClass();
        clazz.getMethod("objectFieldOffset", Field.class);
        clazz.getMethod("arrayBaseOffset", Class.class);
        clazz.getMethod("arrayIndexScale", Class.class);
        clazz.getMethod("getInt", Object.class, long.class);
        clazz.getMethod("putInt", Object.class, long.class, int.class);
        clazz.getMethod("getLong", Object.class, long.class);
        clazz.getMethod("putLong", Object.class, long.class, long.class);
        clazz.getMethod("getObject", Object.class, long.class);
        clazz.getMethod("putObject", Object.class, long.class, Object.class);
        clazz.getMethod("getByte", Object.class, long.class);
        clazz.getMethod("putByte", Object.class, long.class, byte.class);
        clazz.getMethod("getBoolean", Object.class, long.class);
        clazz.getMethod("putBoolean", Object.class, long.class, boolean.class);
        clazz.getMethod("getFloat", Object.class, long.class);
        clazz.getMethod("putFloat", Object.class, long.class, float.class);
        clazz.getMethod("getDouble", Object.class, long.class);
        clazz.getMethod("putDouble", Object.class, long.class, double.class);
  
        return true;
      } catch (Throwable e) {
        logger.log(
            Level.WARNING,
            "platform method missing - proto runtime falling back to safer methods: " + e);
      }
      return false;
    }
  
    private static boolean supportsUnsafeByteBufferOperations() {
      if (UNSAFE == null) {
        return false;
      }
      try {
        Class<?> clazz = UNSAFE.getClass();
        // Methods for getting direct buffer address.
        clazz.getMethod("objectFieldOffset", Field.class);
        clazz.getMethod("getLong", Object.class, long.class);
  
        if (bufferAddressField() == null) {
          return false;
        }
  
        clazz.getMethod("getByte", long.class);
        clazz.getMethod("putByte", long.class, byte.class);
        clazz.getMethod("getInt", long.class);
        clazz.getMethod("putInt", long.class, int.class);
        clazz.getMethod("getLong", long.class);
        clazz.getMethod("putLong", long.class, long.class);
        clazz.getMethod("copyMemory", long.class, long.class, long.class);
        clazz.getMethod("copyMemory", Object.class, long.class, Object.class, long.class, long.class);
        return true;
      } catch (Throwable e) {
        logger.log(
            Level.WARNING,
            "platform method missing - proto runtime falling back to safer methods: " + e);
      }
      return false;
    }
  
  
    /** Finds the address field within a direct {@link Buffer}. */
    private static Field bufferAddressField() {
      Field field = field(Buffer.class, "address");
      return field != null && field.getType() == long.class ? field : null;
    }
  
    /** Finds the value field within a {@link String}. */
    private static Field stringValueField() {
      Field field = field(String.class, "value");
      return field != null && field.getType() == char[].class ? field : null;
    }
  
    /**
     * Returns the offset of the provided field, or {@code -1} if {@code sun.misc.Unsafe} is not
     * available.
     */
    private static long fieldOffset(Field field) {
      return field == null || MEMORY_ACCESSOR == null ? -1 : MEMORY_ACCESSOR.objectFieldOffset(field);
    }
  
    /**
     * Gets the field with the given name within the class, or {@code null} if not found. If found,
     * the field is made accessible.
     */
    private static Field field(Class<?> clazz, String fieldName) {
      Field field;
      try {
        field = clazz.getDeclaredField(fieldName);
        field.setAccessible(true);
      } catch (Throwable t) {
        // Failed to access the fields.
        field = null;
      }
      return field;
    }
  
    private abstract static class MemoryAccessor {
  
      sun.misc.Unsafe unsafe;
  
      MemoryAccessor(sun.misc.Unsafe unsafe) {
        this.unsafe = unsafe;
      }
  
      public final long objectFieldOffset(Field field) {
        return unsafe.objectFieldOffset(field);
      }
  
      public abstract byte getByte(Object target, long offset);
  
      public abstract void putByte(Object target, long offset, byte value);
  
      public final int getInt(Object target, long offset) {
        return unsafe.getInt(target, offset);
      }
  
      public final void putInt(Object target, long offset, int value) {
        unsafe.putInt(target, offset, value);
      }
  
      public final long getLong(Object target, long offset) {
        return unsafe.getLong(target, offset);
      }
  
      public final void putLong(Object target, long offset, long value) {
        unsafe.putLong(target, offset, value);
      }
  
      public abstract boolean getBoolean(Object target, long offset);
  
      public abstract void putBoolean(Object target, long offset, boolean value);
  
      public abstract float getFloat(Object target, long offset);
  
      public abstract void putFloat(Object target, long offset, float value);
  
      public abstract double getDouble(Object target, long offset);
  
      public abstract void putDouble(Object target, long offset, double value);
  
      public final Object getObject(Object target, long offset) {
        return unsafe.getObject(target, offset);
      }
  
      public final void putObject(Object target, long offset, Object value) {
        unsafe.putObject(target, offset, value);
      }
  
      public final int arrayBaseOffset(Class<?> clazz) {
        return unsafe.arrayBaseOffset(clazz);
      }
  
      public final int arrayIndexScale(Class<?> clazz) {
        return unsafe.arrayIndexScale(clazz);
      }
  
      public abstract byte getByte(long address);
  
      public abstract void putByte(long address, byte value);
  
      public abstract int getInt(long address);
  
      public abstract void putInt(long address, int value);
  
      public abstract long getLong(long address);
  
      public abstract void putLong(long address, long value);
  
      public abstract Object getStaticObject(Field field);
      
      public abstract void copyMemory(long srcOffset, byte[] target, long targetIndex, long length);
      
      public abstract void copyMemory(byte[] src, long srcIndex, long targetOffset, long length);
    }
  
    private static final class JvmMemoryAccessor extends MemoryAccessor {
  
      JvmMemoryAccessor(sun.misc.Unsafe unsafe) {
        super(unsafe);
      }
  
      @Override
      public byte getByte(long address) {
        return unsafe.getByte(address);
      }
  
      @Override
      public void putByte(long address, byte value) {
        unsafe.putByte(address, value);
      }
  
      @Override
      public int getInt(long address) {
        return unsafe.getInt(address);
      }
  
      @Override
      public void putInt(long address, int value) {
        unsafe.putInt(address, value);
      }
  
      @Override
      public long getLong(long address) {
        return unsafe.getLong(address);
      }
  
      @Override
      public void putLong(long address, long value) {
        unsafe.putLong(address, value);
      }
  
      @Override
      public byte getByte(Object target, long offset) {
        return unsafe.getByte(target, offset);
      }
  
      @Override
      public void putByte(Object target, long offset, byte value) {
        unsafe.putByte(target, offset, value);
      }
  
      @Override
      public boolean getBoolean(Object target, long offset) {
        return unsafe.getBoolean(target, offset);
      }
  
      @Override
      public void putBoolean(Object target, long offset, boolean value) {
        unsafe.putBoolean(target, offset, value);
      }
  
      @Override
      public float getFloat(Object target, long offset) {
        return unsafe.getFloat(target, offset);
      }
  
      @Override
      public void putFloat(Object target, long offset, float value) {
        unsafe.putFloat(target, offset, value);
      }
  
      @Override
      public double getDouble(Object target, long offset) {
        return unsafe.getDouble(target, offset);
      }
  
      @Override
      public void putDouble(Object target, long offset, double value) {
        unsafe.putDouble(target, offset, value);
      }
      
      @Override 
      public void copyMemory(long srcOffset, byte[] target, long targetIndex, long length) {
        unsafe.copyMemory(null, srcOffset, target, BYTE_ARRAY_BASE_OFFSET + targetIndex, length);
      }
      
      @Override
      public void copyMemory(byte[] src, long srcIndex, long targetOffset, long length) {
        unsafe.copyMemory(src, BYTE_ARRAY_BASE_OFFSET + srcIndex, null, targetOffset, length);
      }
  
      @Override
      public Object getStaticObject(Field field) {
        return getObject(unsafe.staticFieldBase(field), unsafe.staticFieldOffset(field));
      }
    }
  
  }
  